1. Field of the Invention
This invention relates to a superconducting, reversible, variable inductor capable of electromagnetically varying inductance in a reversible manner. For instance, a superconducting, reversible, variable inductor according to this invention can be applied to various modulators of high speed response type, variable frequency oscilators and the like.
2. Description of Prior Art
There have been known two types of superconductors. One of the superconductors is a Type I superconductor. The Type I superconductor exhibits complete diamagnetism and superconductivity in the range of critical magnetic field Hc or less, and ordinary conductivity in the range of the critical magnetic field Hc or more. The other is a Type II superconductor. The Type II superconductor exhibits complete diamagnetism and superconductivity in the range of a lower critical magnetic field Hc1 or less, superconductivity and incomplete diamagnetism, namely a mixed state, in the range of from the lower critical range Hc1 to an upper critical magnetic field Hc2 or less, and ordinary conductivity and paramagnetism in the range of the upper critical magnetic field Hc2 or more.
Conventionally, superconducting modulators have been proposed, in which a coil is wound around a core made of a Type I superconductor. The inductance of the modulators is varied by applying heat pulses to the core.
Further, there have been known variable inductors whose inductance is varied linearly by moving a magnetic core, such as a ferrite core. Other than the above described variable inductors, there have been known variable inductors whose inductance is varied non-linearly by a magnetically saturable a magnetic core thereof.
However, the conventional superconducting modulators have problems of low speed response due to the slow heat conduction and bad controllability caused by using heat as a control factor. These problems result from the fact that the conventional superconducting modulators utilize the heat pulses applied repeatedly to the core, thereby effecting the change from the complete diamagnetism to the paramagnetism, or vice versa.
The conventional variable inductors utilizing the movement of the magnetic core have complicated structures. In addition, the variable inductors cannot vary the inductance at a high speed. Further, it is hard to apply the other conventional variable inductors emplying the magnetic saturation of the magnetic core to circuits for linear applications.